Interleukin 2 (IL 2), also known as T cell growth factor, is a lymphokine produced by amplifier T lymphocytes. The specific stimulation of immune T cells with antigen "activates" T cells to express IL 2 receptors. IL 2 binds avidly to its receptor and induces T cell replication. In vitro, IL 2 induces the proliferation of "activated" T cells capable of mediating a variety of differentiated effector functions. Similarly, we have recently shown that the administration of purified IL 2 in vivo can induce the growth of antigen-activated T cells, and thereby augment specific T cell function. Thus, by virtue of its potent action on lymphoid cells bearing IL 2 receptors, IL 2 may have significant therapeutic potential as a pharmacologic agent to augment specific T cell immunity in vivo. The specific aims of the laboratory project are: to determine the pharmacologic potential of exogenous IL 2 by defining the influence of dose, route, and timing in inducing the growth and augmenting the function of specifically immune donor T cells in vivo; and to determine the effect of the IL 2 regimens developed on immune responses in both normal and immunodeficient mice.